Run Ensemble on Windows (I don't know if the bug is specific to this platform). Move mouse over one of the rounded rectangles to the right. The rectangle should be highlighted and animation inside should start playing. However, after a few seconds or even less, the rectangle gets unhovered and animation stops, while the mouse cursor is still over there. Then it may or not be hovered again.

It's unknown if this is a problem with Ensemble or SceneGraph. However, if I comment the following line (*) in the code below (javafx.scene.Scene, MouseHandler inner class):

        private void pulse() {
            if (hover && lastEvent != null) {
                //Shouldn't run user code directly. User can call stage.showAndWait() and block the pulse.
(*) Platform.runLater(pickProcess);
            }
        }

the problem disappears.